Turbine bucket



mama Man. a reaa UNITED stares morzwnnrn, or a 1 TURBINE BUG 11o Erawing.

Application filed August 23, 1921. Serial No. 494,649.

(@530. ER til? JPRUVESIONS F '1 ACT OF MARCH 3, 1921, 41 STAT. 1., 1818.)

To all whom it may concern:

Be it known that I, I-IANs HOLZWARTH, a citizen of Germany, and resident of-Mulheim, Germany, have invented certain new 5 and useful Improvements in Turbine Buckets (for which I have filed applications in Germany, January 10, 1919; England, June 30, 1920, Patent No. 145,639; France, July 10, 1920, Patent No. 520,375; Holland, Jul

to 10, 1920; Italy, June 29, 1920), of whic the following is a specification.

lMly invention relates to the construction of buckets for steam and gas turbines. The operative effects upon the buckets of large steam turbines operating at very high driving temperatures and particularly upon the buckets of gas turbines are entirely difierent from those upon the buckets of steam turbines of normal operation and moderate at temperatures. In explosion turbines the force of the explosion upon the buckets is,

short and in the nature of a blow, so that said buckets must be of universal strength throughout. On the other" hand, the cen- 2o trifugal force which, is developed requires the utmost economy in mass in the construction of such buckets. The high temperatures to which the first series of buckets in steam turbines and, above all, the buckets in gas or explosion turbines, are subjected,

require the use of specially adapted material and that the strains be moderate in all parts thereof. The particular object of the present invention is to construct the buckets of a novel and eficient material specially adapted to meet and overcome the,-in part, contradictory conditions set forth. My invention will be fully described hereinafter and the features of nbvelty will be pointed out in the ap ended claims. The materia which I use for constructing turbine buckets in accordance with the pres- Y ent invention comprises ingot iron, preferably practically unalloyed and free from' objectionable and harmful mixtures and I relatively poor in carbon and melted in an electric furnace or in a basic Martin furnace. The carbon content is preferably maintained below 0.1%, and vin any case should not materially exceed this point, an

the percentage of manganese present therein ranges approximately from 0.30 to 0.50%;

till

nickel, chrome or other additions are not desirable. A material of the kind described, after a heat treatment at 450, has a stretching or drawing limit of from 1300 to 1500 kg/cm If the calculable, permissible strains resulting from centrifugal force and bending forces do not exceed from 800 to 900 kg/cm the factor of safety is ample with a bucket of good form and a proper jet delivery.

Buckets constructed of the described material with the enumerated points in mind operate efliciently and maintain their form very satisfactorily during the operation of explosion turbines while other materials, and particularly alloyed ingot iron or alloyed steel, do not answer the requirements. In operation, the buckets of the turbine, when operated without water injection and only with air cooling, automatically become covered with a ermanent protectin skin of ferrous oxide, t at is to say, a com bination of iron oxygen, which prevents rust and maintains the outer surface of the bucket permanently smooth and polished.

Various changes in the specific form described may be made within the scope of the claims without departing from the spirit of my invention.

I claim:

1. A bucket for gas and steam turbines adapted for high temperatures made of practically unalloyed iron having a low carbon content.

2. A bucket for gas and steam turbines adapted for high temperatures consisting of practically una loyed iron having a low'carbon content and free from nickel, chrome or other additions not including manganese.

3. A bucket for gas and steam turbines adapted for high temperatures consisting of practically una loyed lIOIl having a low caron content and a manganese content ranging from about 0.30 to 0.50%.

4. A bucket for gas and steam turbines adapted for high temperatures made of practically unalloyed iron having a carbon content not exceeding 0.1%.

In testimony whereof I have hereunto set my hand. 

